This past Saturday I picked up a 3/4 Ton 57 NAPCO chassis with auxilliary springs and it has a spacer between the main and auxilliary leaves that appears to be the same thickness as the photo I've been checking out. I will take photos and measurements tonight (6-13-2011). It will be interesting to get the measurement. These spacers appear to be sheared for length and width is the same as the spring length.

Joe (28 Graham)